Northwest NEWS

April 10, 2000

Kenmore residents needed to monitor heron population

The Great Blue Heron is a colonial nester, which means they create large colonies of nests in several locations. King County colonies typically accommodate up to 100 birds, with numbers reaching 600 elsewhere in the region.

Normally, they return to the same colony every year in January or early February to begin mating, and do not disperse until the end of July. But lately, they have not been returning to their colonies the following year.

Though biologists began noticing this growing trend approximately five years ago, they have been unable to determine the cause. The identification of a decline in Puget Sound heron populations is currently based on data collected through individual colony monitoring. However, there has been no systematic monitoring of the entire region.

"The King County Wildlife Program monitors colonies, but we need increased community involvement to enhance our existing data," says Stenberg. "If you live near a heron colony, we'd like to know what you saw last year and what is going on this year--how many nests are there and when were they occupied," she says.

The increased population of the bald eagle, a natural predator of the heron, may be a factor. The eagles may prey on heron eggs and chicks and, once the nest is exposed, it also creates an opportunistic situation for crows, another bird population that is increasing in urban areas.

Urbanization has created a lack of heron habitat, resulting in smaller nesting colonies. Colony abandonment during the nesting season may be due to a decline in food supplies, such as small fish and amphibians, for the herons.

One of the larger local colonies is at the Kenmore Park & Ride lot. People should stay at least 600 feet from a colony; an observer is too close if the birds fly off their nests. Binoculars or a spotting scope are best for observing herons from a distance.